Build materials for 3D printing

ABSTRACT

Polymerizable liquids are described herein which, in some embodiments, can produce 3D printed articles of high resolution and desirable mechanical properties. In one aspect, a polymerizable liquid comprises an acrylate component, a polymeric additive, and a monomeric curing agent, wherein the acrylate component and monomeric curing agent are copolymerizable upon exposure to light. In being copolymerizable, the acrylate component and monomeric curing agent can form a copolymer. As described father herein, the monomeric curing agent can enable further reaction of the copolymer with one or more crosslinking species to link the copolymer with one more polymeric networks.

RELATED APPLICATION DATA

The present application claims priority pursuant to 35 U.S.C. § 119(e)to U.S. Provisional Patent Application Ser. No. 62/873,486 filed Jul.12, 2019 which is incorporated herein by reference in its entirety.

FIELD

The present invention relates to three-dimensional build materials and,in particular, to polymerizable liquids for use with three-dimensionalprinting systems.

BACKGROUND

3D printers employ build materials, which are also known as inks, toform various 3D objects, articles, or parts in accordance with computergenerated files. In some instances, the build material is solid atambient temperatures and converts to liquid at elevated jettingtemperatures. In other instances, the build material is liquid atambient temperatures.

Build materials can comprise a variety of chemical species. Selection ofchemical species to include in a build material can be selectedaccording to various considerations including, but not limited to,desired chemical and/or mechanical properties of the printed article andoperating parameters of the 3D printing apparatus. For example,ultra-violet (UV) curable acrylate formulations generally can printparts with high resolution on DLP systems. However, in many cases, theresulting parts lack desirable mechanical properties and can be prone tofracture or other degradative pathways.

SUMMARY

In view of the foregoing, polymerizable liquids are described hereinwhich, in some embodiments, can produce 3D printed articles of highresolution and desirable mechanical properties. In one aspect, apolymerizable liquid comprises an acrylate component, a polymericadditive, and a monomeric curing agent, wherein the acrylate componentand monomeric curing agent are copolymerizable upon exposure to light.In being copolymerizable, the acrylate component and monomeric curingagent can form a copolymer. As described further herein, the monomericcuring agent can enable further reaction of the copolymer with one ormore crosslinking species to chemically link the copolymer with one ormore polymeric networks. In some embodiments, the monomeric curing agentenables linking of the copolymer with the polymeric additive. Chemicallinking of polymeric networks can provide 3D printed articles withenhanced mechanical properties. In some embodiments, the polymericadditive comprises one or more thermoplastics, such as a multiblockcopolymer. In some cases, the multiblock copolymer comprisespolyurethane.

In another aspect, methods of printing three-dimensional articles aredescribed herein. In some embodiments, a method of printing athree-dimensional article comprises providing a polymerizable liquidcomprising an acrylate component, a polymeric additive, and a monomericcuring agent. The polymerizable liquid is irradiated with light to formthe article, the article comprising a polymeric composite materialincluding the polymeric additive and copolymer comprising the acrylatecomponent and monomeric curing agent. In some embodiments, the articleis formed via a layer-by-layer process, wherein layer formation isadministered via deposition and irradiation of a layer of thepolymerizable liquid.

Additionally, the polymerizable liquid may further comprise acrosslinking component, wherein the monomeric curing agent of thecopolymer is operable to initiate crosslinking reactions with thecrosslinking component. The monomeric curing agent, in some embodiments,can initiate crosslinking reactions to link the copolymer with one morepolymeric species in the polymerizable liquid. For example, themonomeric curing agent can initiate reactions to crosslink the copolymerwith the polymeric additive. In some embodiments, crosslinking reactionsare initiated subsequent to formation of the articles. The article, forexample, can be heated or irradiated to initiate crosslinking or curingvia the monomeric curing agent. Crosslinking or curing can induce acolor change in the article, in some embodiments. Notably, such colorchange may occur in the absence of any pigment added to thepolymerizable liquid.

In some embodiments, the polymer additive is not present in thepolymerizable liquid. In such embodiments, the polymerizable liquidcomprises the acrylate component, monomeric curing, and crosslinkingcomponent. Irradiation of the polymeric liquid can form a copolymerbetween the acrylate component and monomeric curing agent. As describedherein, the monomeric curing agent of the copolymer can subsequentlyinitiate reactions with the crosslinking component via thermal and/orlight stimulation.

In another aspect, a polymerizable liquid comprises an acrylatecomponent, a polymeric additive, and a monomeric solvent for thepolymeric additive, wherein the monomeric solvent and acrylate componentare copolymerizable upon exposure to light. The monomeric solvent isoperable to partially solubilize or fully solubilize the polymericadditive in the polymerizable liquid. Accordingly, the monomeric solventpermits incorporation of polymeric materials into the polymerizableliquid that would otherwise phase separate in a mixture comprising theacrylate component. In some embodiments, for example, the polymericadditive comprises one or more thermoplastics. The thermoplastics cancomprise multiblock copolymer, in some embodiments.

In a further aspect, a method of printing a three-dimensional articlecomprises providing a polymerizable liquid comprising an acrylatecomponent, a polymeric additive, and a monomeric solvent for thepolymeric additive. The polymerizable liquid is irradiated with light toform the article, the article comprising a polymeric composite materialincluding the polymeric additive and copolymer comprising the acrylatecomponent and monomeric solvent. In some embodiments, the article isformed via a layer-by-layer process, wherein layer formation isadministered via deposition and irradiation of a layer of thepolymerizable liquid.

These and other embodiments are further described in the followingdetailed description.

DETAILED DESCRIPTION

Embodiments described herein can be understood more readily by referenceto the following detailed description and examples. Elements, apparatusand methods described herein, however, are not limited to the specificembodiments presented in the detailed description and examples. Itshould be recognized that these embodiments are merely illustrative ofthe principles of the present invention. Numerous modifications andadaptations will be readily apparent to those of skill in the artwithout departing from the spirit and scope of the invention.

In addition, all ranges disclosed herein are to be understood toencompass any and all subranges subsumed therein. For example, a statedrange of “1.0 to 10.0” should be considered to include any and allsubranges beginning with a minimum value of 1.0 or more and ending witha maximum value of 10.0 or less, e.g., 1.0 to 5.3, or 4.7 to 10.0, or3.6 to 7.9.

All ranges disclosed herein are also to be considered to include the endpoints of the range, unless expressly stated otherwise. For example, arange of “between 5 and 10” should generally be considered to includethe end points 5 and 10.

Further, when the phrase “up to” is used in connection with an amount orquantity, it is to be understood that the amount is at least adetectable amount or quantity. For example, a material present in anamount “up to” a specified amount can be present from a detectableamount and up to and including the specified amount.

The terms “three-dimensional printing system,” “three-dimensionalprinter,” “printing,” and the like generally describe various solidfreeform fabrication techniques for making three-dimensional articles orobjects by selective deposition, jetting, fused deposition modeling,multijet modeling, and other additive manufacturing techniques now knownin the art or that may be known in the future that use a build materialor ink to fabricate three-dimensional objects.

In one aspect, polymerizable liquids for use in 3D printing applicationsare described herein. The polymerizable liquids, for example, can beemployed in DLP, SLA, and MJP printing applications, in someembodiments. A polymerizable liquid comprises an acrylate component, apolymeric additive, and a monomeric curing agent, wherein the acrylatecomponent and monomeric curing agent are copolymerizable upon exposureto light. In being copolymerizable, the acrylate component and monomericcuring agent can form a copolymer.

The acrylate component can comprise one or a mixture of lightpolymerizable acrylate species. In some embodiments, for example, theacrylate component can comprise acrylate monomer, acrylate oligomer, ormixtures thereof. As known to the skilled artisan, a monomer is a singlestructural unit of a polymer or copolymer and is not an oligomer orpolymer. In contrast, an oligomer comprises a plurality of chemicallylinked monomers. In some embodiments, the acrylate component cancomprise monofunctional acrylates, difunctional acrylates, or mixturesthereof. In some embodiments, for instance, the acrylate componentcomprises methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl(meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, n-hexyl(meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate,n-decyl (meth)acrylate, n-dodecyl (meth)acrylate, 2-hydroxyethyl(meth)acrylate, 2- or 3-hydroxypropyl (meth)acrylate, 2-methoxyethyl(meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2- or 3-ethoxypropyl(meth)acrylate, tetrahydrofurfuryl methacrylate, isobornyl(meth)acrylate, 2-(2-ethoxyethoxy)ethyl acrylate, cyclohexylmethacrylate, 2-phenoxyethyl acrylate, glycidyl acrylate, isodecylacrylate, 2-phenoxyethyl (meth)acrylate, lauryl methacrylate, ormixtures thereof. In some embodiments, the acrylate component comprisesa monofunctional or difunctional aliphatic urethane (meth)acrylate.

The acrylate component, in some embodiments, can comprise one or more ofallyl acrylate, allyl methacrylate, triethylene glycol di(meth)acrylate,tricyclodecane dimethanol diacrylate, and cyclohexane dimethanoldiacrylate. Additionally, in some embodiments, the acrylate componentcomprises diacrylate and/or dimethacrylate esters of aliphatic,cycloaliphatic or aromatic diols, including 1,3- or 1,4-butanediol,neopentyl glycol, 1,6-hexanediol, diethylene glycol, triethylene glycol,tetraethylene glycol, polyethylene glycol, tripropylene glycol,ethoxylated or propoxylated neopentyl glycol,1,4-dihydroxymethylcyclohexane, 2,2-bis(4-hydroxycyclohexyl)propane orbis(4-hydroxycyclohexyl)methane, hydroquinone, 4,4′-dihydroxybiphenyl,bisphenol A, bisphenol F, bisphenol S, ethoxylated or propoxylatedbisphenol A, ethoxylated or propoxylated bisphenol F or ethoxylated orpropoxylated bisphenol S.

Additional non-limiting examples of species suitable for inclusion inthe acrylate component comprise the following: isobornyl acrylate(IBOA), commercially available from SARTOMER under the trade name SR506A; isobornyl methacrylate, commercially available from SARTOMER underthe trade name SR 423A; alkoxylated tetrahydrofurfuryl acrylate,commercially available from SARTOMER under the trade name SR 611;monofunctional urethane acrylate, commercially available from RAHN USAunder the trade name GENOMER 1122; aliphatic urethane diacrylate,commercially available from ALLNEX under the trade name EBECRYL 8402;difunctional aliphatic urethane (meth)acrylate, commercially availablefrom DYMAX under the BR-952 trade designation; triethylene glycoldiacrylate, commercially available from SARTOMER under the trade name SR272; and triethylene glycol dimethacrylate, commercially available fromSARTOMER under the trade name SR 205. Other commercially availablecurable components may also be used. In addition, in some cases, amonofunctional or difunctional acrylate comprises an aliphatic polyesterurethane acrylate oligomer, a urethane (meth)acrylate resin, and/or anacrylate amine oligomeric resin, such as EBECRYL 7100. In someembodiments, the acrylate component comprises one or more acrylatederivatives such as acryloylmorpholine.

The acrylate component can be present in the polymerizable liquid in anyamount consistent with the objectives described herein. In someembodiments, the acrylate component is present in an amount in an amountup to about 90 wt. %, up to about 85 wt. %, up to about 80 wt. %, or upto about 75 wt. %, based on the total weight of the ink in an amount upto about 90 wt. %, up to about 85 wt. %, up to about 80 wt. %, or up toabout 75 wt. %, based on the total weight of the polymerizable liquid.For example, the acrylate component can be present in an amount of 20-90wt. %. In some embodiments, the polymerizable liquid comprises about20-70 wt. %, 40-90 wt. %, 55-90 wt. %, 60-90 wt. %, 65-90 wt. %, 65-85wt. %, 70-90 wt. %, 75-90 wt. %, or 80-90 wt. % acrylate component,based on the total weight of the ink. Moreover, in some embodiments, thepolymerizable liquid comprises 30-45 wt. % or 50-70 wt. % acrylatecomponent, based on the total weight of the ink.

In addition to the monofunctional and difunctional acrylate speciescomponents described above, it is also possible, in some cases, toinclude trifunctional or higher functional acrylate species in apolymerizable liquid described herein. For example, in some instances,one or more tri(meth)acrylates may be used. However, it is to beunderstood that the functionality (i.e., mono-, di-, tri-, or higherfunctionality) and the molecular weight of the acrylate speciesdescribed herein can be selected to provide a build material having aviscosity suitable for use in a desired 3D printing system. Non-limitingexamples of trifunctional or higher (meth)acrylates that may be suitablefor use in some embodiments described herein include1,1-trimethylolpropane tri(meth)acrylate, ethoxylated or propoxylated1,1,1-trimethylolpropanetri(meth)acrylate, ethoxylated or propoxylatedglycerol tri(meth)acrylate, pentaerythritol monohydroxytri(meth)acrylate, dipentaerythritol monohydroxy penta(meth)acrylate,and bis(trimethylolpropane) tetra(meth)acrylate.

As described herein, the polymerizable liquid also comprises a polymericadditive. Inclusion of a polymeric additive with the acrylate componentcan improve one or more mechanical properties of articles formed fromthe polymerizable liquid via additive manufacturing techniques. In someembodiments, inclusion of the polymeric additive can enhance one or moreof tensile strength, shear strength, flexibility, elongation, heatdeflection temperature and/or impact resistance of the article.

In some cases, polymeric additives described herein comprise one or morethermoplastics or thermoplastic components. Thermoplastics describedherein can comprise multiblock copolymer. In some embodiments, forexample, the polymeric additive comprises a thermoplastic polyurethane(TPU). The thermoplastic polyurethane can be a polyester TPU, apolyether TPU, a polycaprolactone TPU, or mixtures thereof. In somecases, the thermoplastic polyurethane is aromatic (based on isocyanatessuch as MDI) or aliphatic (based on isocyanates such as H12 MDI, HDI,and IPDI). TPU can have hard and soft sequences or domains, where thehard segments are formed from short-chain diols (“chain extenders”), andthe soft segments formed from long-chain diols. The ratios of hard tosoft can be varied, as well as the structure and/or molecular weight ofthe diols, to produce TPU variants having a wide range of physicalproperties.

The polymeric additive can be present in the polymerizable liquid in anyamount consistent with the objectives described herein. Amount ofpolymeric additive in the polymerizable liquid can be selected accordingto several considerations including, but not limited to, chemicalidentity of the acrylate component, chemical identity of the polymericadditive, and/or desired mechanical properties of the resultant articlesformed from the polymerizable liquid via additive manufacturing. In someembodiments, the polymeric additive is present in a build material in anamount of 5-50 wt. %, 10-40 wt. %, 15-35 wt. %, 20-30 wt. %, 5-25 wt. %,5-20 wt. %, 5-15 wt. %, 5-10 wt. %, 10-25 wt. %, 30-40 wt. %, 14-20 wt.%, 5 wt. %, 7 wt. %, 9 wt. %, 10 wt. %, 12 wt. %, 14 wt. %, 16 wt. %, 18wt. %, 20 wt. %, 22 wt. %, 24 wt. %, 26 wt. %, 28 wt. %, or 30 wt. %,

In addition to the acrylate component and polymeric additive, thepolymerizable liquid also comprises a monomeric curing agent. Theacrylate component and monomeric curing agent are copolymerizable uponexposure to light. In being copolymerizable, the acrylate component andmonomeric curing agent form a copolymer. Notably, the monomeric curingagent can enable further reaction of the copolymer with one or morecrosslinking species to link the copolymer with one or more polymericnetworks. In some embodiments, the monomeric curing agent enableslinking of the copolymer with the polymeric additive. Chemical linkingof polymeric networks can provide 3D printed articles with enhancedmechanical properties. Additionally, chemical linking between polymericnetworks presents a fundamentally different structure compared topolymeric networks that physically interpenetrate with one another.

Subsequent to formation of a copolymer with the acrylate component, themonomeric curing agent can further react with one or more crosslinkingspecies. In some embodiments, heat or light is applied to stimulatereaction between the monomeric curing agent and crosslinking species.The monomeric curing agent, in some embodiments, can serve as aninitiator or catalyst for crosslinking reactions. The monomeric curingagent can comprise any species operable to copolymerize with theacrylate component while maintaining functionality for participating incrosslinking reactions subsequent to copolymer formation. In someembodiments, the monomeric curing agent serves as an initiator orcatalyst for the crosslinking reactions. In some embodiments, forexample, the monomeric curing agent comprises one or more imidazoles,wherein the imidazoles are operable for copolymerization with theacrylate component. In one embodiment, for example, the monomeric curingagent comprises vinyl-imidazole. Epoxy and/or isocyanate crosslinkingspecies can react with the imidazole to form crosslinks between theimidazole-acrylate copolymer and polymeric additive or other species inthe polymerizable liquid, in some embodiments. In some cases,unsaturated nitrogen in the imidazole ring can act as an anionicinitiator and form a 1:1 epoxy-imidazole adduct, which can then furtherpolymerize by reacting with another epoxy resin crosslinking component.

In some embodiments, the complete article or a section thereof is formedprior initiation of reaction between the monomeric curing agent andcrosslinking component. For example, the article can be printed viacopolymerization of the acrylate component and monomeric curing agent.Subsequent formation, the article can be heated or irradiated toinitiate reaction between the monomeric curing agent and crosslinkingcomponent.

Additionally, in some embodiments, the monomeric curing agent canpartially solubilize or fully solubilize the polymeric additive.Accordingly, the monomeric curing agent can permit incorporation ofpolymeric materials into the polymerizable liquid that would otherwisephase separate in a mixture comprising the acrylate component. In someembodiments, for example, the monomeric curing agent can be a solventfor one or more TPU species described above.

The monomeric curing agent can be present in the polymerizable liquid inany desired amount. Amount of monomeric curing agent can be selectedaccording to several considerations including, but not limited to, thechemical identity of the acrylate component and the desired amount ofcrosslinking between copolymer incorporating the monomeric curing agentand one or more polymeric species in the polymerizable liquid.Generally, the monomeric curing agent can be present in thepolymerizable liquid in an amount of 2 to 20 weight percent.

A crosslinking component for reaction with the monomeric curing agentcan comprise an epoxy resin, an isocyanate component, a polyolcomponent, or mixtures thereof. Any epoxy resin not inconsistent withthe objectives of this disclosure can be used, such as epoxidizedbisphenol A, epoxidized bisphenol F, epoxidized phenol Novolak epoxy,epoxidized cresol Novolak epoxy, brominated multifunctional epoxy,multifunctional epoxy resin (TGMDA or TGPAP), cyclo-aliphatic epoxy,epoxidized polypropylene glycol carrier (weight average molecular weight400, 1000, or 2000), epoxidized phenoxyethylacrylate carrier, or anycombination thereof. Any isocyanate component not inconsistent with theobjectives of this disclosure can be used. Exemplary isocyanatecomponents include aliphatic diisocyanates such as hexamethylenediisocyanate (HDI), methylene dicyclohexyl diisocyanate (HMDI) orhydrogenated MDI, isophorone diisocyanate (IPDI). Any polyol componentnot inconsistent with the objectives of this disclosure can also beused.

In some embodiments, a crosslinking component can be coated on aparticle to form a core-shell configuration. Particles coated withcrosslinking component can have any desired chemical identity. Chemicalidentity of the particles can be selected according to severalconsiderations including, but not limited to, the identity of theacrylate component and desired mechanical properties of the resultantarticle formed from the polymerizable liquid via additive manufacturing.In some embodiments, the particles comprise thermoplastic or thermosetmaterials. Alternatively, the particles can comprise elastomer. In someembodiments, for example, coated particles are commercially availablefrom Kaneka Texas Corporation under the Kane Ace® MX trade designation.Particle coatings are operable to crosslink with the acrylate copolymercomprising the monomeric curing agent. The monomeric curing agent, forexample, can react with the crosslinking component of the particles tochemically link the coated particles to the acrylate copolymerincorporating the monomeric curing agent.

The crosslinking component can be present in the polymerizable liquid inany desired amount. Amount of crosslinking component can be selectedaccording to several considerations including, but not limited to, theidentity of the copolymer comprising the acrylate component andmonomeric curing agent, identity of the crosslinking component, and/ordesired amount of crosslinking. Generally, the crosslinking componentcan be present in the polymerizable liquid in an amount of 15-50 weightpercent.

In some embodiments, the polymerizable liquid does not include thepolymeric component. The polymerizable liquid, for example, can comprisethe acrylate component, the crosslinking component, and the monomericcuring agent, wherein the acrylate component and monomeric curing agentare copolymerizable upon exposure to light. In such embodiments, theacrylate component and monomeric curing agent form a copolymer. Asdescribed herein, the monomeric curing agent of the copolymer cansubsequently react with species of the crosslinking component. In thisway, the copolymer comprising the monomeric curing agent and acrylatecomponent is chemically linked with one or more polymeric networksformed by the crosslinking component. The monomeric curing agent, insome embodiments, is activated by heat or light to react with thecrosslinking component. The monomeric curing agent, for example, can bea catalyst or initiator for reaction and crosslinking with thecrosslinking component.

The polymerizable liquid also comprises a photoinitiator component forinitiating copolymerization of the acrylate component and monomericcuring agent upon exposure to light. Any photoinitiator not inconsistentwith the objectives of the present disclosure can be used. In someembodiments, a photoinitiator comprises an alpha-cleavage type(unimolecular decomposition process) photoinitiator or a hydrogenabstraction photosensitizer-tertiary amine synergist, operable to absorblight preferably between about 250 nm and about 420 nm or between about300 nm and about 385 nm, to yield free radical(s).

Examples of alpha cleavage photoinitiators are Irgacure 184 (CAS947-19-3), Irgacure 369 (CAS 119313-12-1), and Irgacure 819 (CAS162881-26-7). An example of a photosensitizer-amine combination isDarocur BP (CAS 119-61-9) with diethylaminoethylmethacrylate.

In addition, in some instances, suitable photoinitiators comprisebenzoins, including benzoin, benzoin ethers, such as benzoin methylether, benzoin ethyl ether and benzoin isopropyl ether, benzoin phenylether and benzoin acetate, acetophenones, including acetophenone,2,2-dimethoxyacetophenone and 1,1-dichloroacetophenone, benzil, benzilketals, such as benzil dimethyl ketal and benzil diethyl ketal,anthraquinones, including 2-methylanthraquinone, 2-ethylanthraquinone,2-tert-butylanthraquinone, 1-chloroanthraquinone and2-amylanthraquinone, triphenylphosphine, benzoylphosphine oxides, forexample 2,4,6-trimethylbenzoyldiphenylphosphine oxide (Lucirin TPO),benzophenones, such as benzophenone and4,4′-bis(N,N′-dimethylamino)benzophenone, thioxanthones and xanthones,acridine derivatives, phenazine derivatives, quinoxaline derivatives or1-phenyl-1,2-propanedione, 2-O-benzoyl oxime, 1-aminophenyl ketones or1-hydroxyphenyl ketones, such as 1-hydroxycyclohexyl phenyl ketone,phenyl 1-hydroxyisopropyl ketone and 4-isopropylphenyl1-hydroxyisopropyl ketone.

Suitable photoinitiators can also comprise those operable for use with aHeCd laser radiation source, including acetophenones,2,2-dialkoxybenzophenones and 1-hydroxyphenyl ketones, such as1-hydroxycyclohexyl phenyl ketone or 2-hydroxyisopropyl phenyl ketone(=2-hydroxy-2,2-dimethylacetophenone). Additionally, in some cases,suitable photoinitiators comprise those operable for use with an Arlaser radiation source including benzil ketals, such as benzil dimethylketal. In some embodiments, a photoinitiator comprises anα-hydroxyphenyl ketone, benzil dimethyl ketal or2,4,6-trimethylbenzoyldiphenylphosphine oxide or a mixture thereof.

Another class of suitable photoinitiators, in some instances, comprisesionic dye-counter ion compounds capable of absorbing actinic radiationand generating free radicals for polymerization initiation. In someembodiments, polymerizable liquids containing ionic dye-counter ioncompounds can be polymerized upon exposure to visible light within theadjustable wavelength range of about 400 nm to about 700 nm. Ionicdye-counter ion compounds and their mode of operation are disclosed inEP-A-0 223 587 and U.S. Pat. Nos. 4,751,102; 4,772,530; and 4,772,541.

A photoinitiator can be present in a polymerizable liquid describedherein in any amount not inconsistent with the objectives of the presentdisclosure. In some embodiments, a photoinitiator is present in anamount of up to about 5 wt. %, based on the total weight of thepolymerizable liquid. In some cases, a photoinitiator is present in anamount ranging from about 0.1 wt. % to about 5 wt. %.

Moreover, in some embodiments, a polymerizable liquid described hereincan further comprise one or more sensitizers. A sensitizer can be addedto increase the effectiveness of one or more photoinitiators that mayalso be present. Any sensitizer not inconsistent with the objectives ofthe present disclosure may be used. In some cases, a sensitizercomprises isopropylthioxanthone (ITX) or 2-chlorothioxanthone (CTX).

A sensitizer can be present in the polymerizable liquid in any amountnot inconsistent with the objectives of the present disclosure. In someembodiments, a sensitizer is present in an amount ranging from about 0.1wt. % to about 2 wt. % or from about 0.5 wt. % to about 1 wt. %, basedon the total weight of the polymerizable liquid.

In some embodiments, one or more UV-absorbers and/or light stabilizerscan be present in the polymerizable liquid. In some embodiments, forexample, one or more UV-absorbers and/or light stabilizers can bepresent in an amount of 0.1-2 wt. %, based on the total weight of thepolymerizable liquid. In some embodiments, UV-absorbers and/or lightstabilizers are commercially available from BASF of Florham Park, N.J.under the TINUVIN® trade-designation.

In another aspect, methods of printing a 3D article or object aredescribed herein. Methods of printing a 3D article or object can includeforming the 3D article from a plurality of layers of a polymerizableliquid described herein in a layer-by-layer manner. Any polymerizablematerial described herein may be used in the fabrication of the articleby additive manufacturing.

In some embodiments, a method of printing a three-dimensional articlecomprises providing a polymerizable liquid comprising an acrylatecomponent, a polymeric additive, and a monomeric curing agent. Thepolymerizable liquid is irradiated with light to form the article, thearticle comprising a polymeric composite material including thepolymeric additive and copolymer comprising the acrylate component andmonomeric curing agent. In some embodiments, the article is formed via alayer-by-layer process wherein layer formation is administered viadeposition and irradiation of a layer of the polymerizable liquid. Theacrylate component, polymeric additive and monomeric curing agent canhave any composition and/or properties described herein. In someembodiments, for example, the polymeric additive comprises one or moreTPU species and the monomeric curing agent comprises one or morepolymerizable imidazole species.

As described herein, the polymerizable liquid may further comprise acrosslinking component. The crosslinking component can have anycomposition and/or properties described herein. In some embodiments, forexample, the crosslinking component comprises epoxy resin, an isocyanatecomponent, a polyol component, or mixtures thereof. Additionally, thecrosslinking component can be coated on particles as described herein.In embodiments where the crosslinking component is present in thepolymerizable liquid, a method of printing a 3D article can furthercomprise crosslinking the crosslinking component with the copolymercomprising the acrylate component and monomeric curing agent. In someembodiments, the crosslinking is initiated by reaction of the monomericcuring agent with the crosslinking component. The monomeric curingagent, for example, can be a catalyst or initiator of the crosslinkingreaction. Heat or light can be applied after formation of the copolymercomprising the monomeric curing agent and acrylate component to initiatecrosslinking between the copolymer and crosslinking component. In someembodiments, the crosslinking component chemically binds the copolymerto one or more polymer networks. For example, the crosslinking componentcan chemically bind the copolymer comprising the acrylate component andmonomeric curing agent to the polymeric additive of the polymerizableliquid. In particular embodiments, the crosslinking component canchemically bind the copolymer to one or more TPU species of thepolymerizable liquid. Alternatively, the crosslinking component canchemically bind the copolymer comprising the acrylate component andmonomeric curing agent to particles coated with the crosslinkingcomponent.

In some embodiments, the three-dimensional article printed from thepolymerizable liquid is black in color following crosslinking reactionbetween the monomeric curing agent and crosslinking component. In suchembodiments, the polymerizable liquid does not comprise or substantiallycomprise any pigment species. Accordingly, a desirable black color canbe achieved with materials and systems described herein without the needto add pigment to the polymerizable liquid. The black color of thethree-dimensional article can be homogeneous or substantiallyhomogeneous throughout the article, in some embodiments.

In another aspect, a polymerizable liquid comprises an acrylatecomponent, a polymeric additive, and a monomeric solvent for thepolymeric additive, wherein the monomeric solvent and acrylate componentare copolymerizable upon exposure to light. In some embodiments, theacrylate component and polymeric additive can comprise any compositionand/or properties described hereinabove.

The monomeric solvent is operable to partially solubilize or fullysolubilize the polymeric additive in the polymerizable liquid.Accordingly, the monomeric solvent permits incorporation of polymericmaterials into the polymerizable liquid that would otherwise phaseseparate in a mixture comprising the acrylate component. In someembodiments, for example, the polymeric additive comprises one or morethermoplastics, including any of the TPU species described herein. Insome embodiments, the monomeric solvent is operable to partiallysolubilize or fully solubilize one or more TPU species in thepolymerizable liquid. In some embodiments, the monomeric solventcomprises N-vinyl caprolactam, N-vinyl imidazole, N-vinylpyrrolidone,acrylate monomer, or mixtures thereof.

The monomeric solvent can be present in the polymerizable liquid in anyamount consistent with the objectives described herein. Amount ofmonomeric solvent in the polymerizable liquid can be selected accordingto several considerations including, but not limited to, the identity ofthe polymeric additive, the amount of polymeric additive, and/or theidentity of the acrylate component. Generally, the monomeric solvent canbe present in an amount of 2-20 weight percent of the polymerizableliquid.

In a further aspect, a method of printing a three-dimensional articlecomprises providing a polymerizable liquid comprising an acrylatecomponent, a polymeric additive, and a monomeric solvent for thepolymeric additive. The polymerizable liquid is irradiated with light toform the article, the article comprising a polymeric composite materialincluding the polymeric additive and copolymer comprising the acrylatecomponent and monomeric solvent. In some embodiments, the article isformed via a layer-by-layer process, wherein layer formation isadministered via deposition and irradiation of a layer of thepolymerizable liquid.

In some embodiments, layers of polymerizable liquids can be depositedaccording to an image of the 3D article in a computer readable formatduring formation of the three-dimensional article. The polymerizableliquid can be deposited according to preselected computer aided design(CAD) parameters. Moreover, in some cases, one or more layers of thepolymerizable liquid described herein has a thickness of about 10 μm toabout 100 μm, about 10 μm to about 80 μm, about 10 μm to about 50 μm,about 20 μm to about 100 μm, about 20 μm to about 80 μm, or about 20 μmto about 40 μm. Other thicknesses are also possible.

Additionally, it is to be understood that methods of printing a 3Darticle described herein can include so-called “multi-jet” or“stereolithography” 3D printing methods. For example, in some instances,a multi-jet method of printing a 3D article comprises selectivelydepositing layers of a polymerizable liquid described herein onto asubstrate, such as a build pad of a 3D printing system. In addition, insome embodiments, a method described herein further comprises supportingat least one of the layers of the polymerizable liquid with a supportmaterial. Any support material not inconsistent with the objectives ofthe present disclosure may be used.

It is also possible to form a 3D article from a polymerizable liquiddescribed herein using stereolithography. For example, in some cases, amethod of printing a 3D article comprises retaining the polymerizableliquid in a container and selectively applying energy to thepolymerizable liquid in the container to solidify at least a portion ofa polymerizable liquid, thereby forming a solidified layer that definesa cross-section of the 3D article. Additionally, a method describedherein can further comprise raising or lowering the solidified layer toprovide a new or second layer of polymerizable liquid, followed by againselectively applying energy to the polymerizable liquid in the containerto solidify at least a portion of the new or second polymerizable liquidthat defines a second cross-section of the 3D article. Further, thefirst and second cross-sections of the 3D article can be bonded oradhered to one another in the z-direction (or build directioncorresponding to the direction of raising or lowering recited above) bythe application of the energy for solidifying the polymerizable liquid.Moreover, selectively applying energy to the polymerizable liquid in thecontainer can comprise applying electromagnetic radiation, such as UVand/or visible radiation, having a sufficient energy to initiatepolymerization of the polymerizable material as described herein. Inaddition, in some cases, raising or lowering a solidified layer ofpolymerizable liquid is carried out using an elevator platform disposedin the container of fluid build material. A method described herein canalso comprise planarizing a new layer of polymerizable liquid providedby raising or lowering an elevator platform. Such planarization can becarried out, in some cases, by a wiper or roller.

In another aspect, printed 3D articles are described herein. In someembodiments, a printed 3D article is formed from any of thepolymerizable liquids described herein. 3D articles formed frompolymerizable liquids described herein can have an impact resistancethat is greater than 1 ft·lb/in., in some embodiments. A 3D article, forexample, can exhibit an impact resistance of 1.1-2 ft·lb/in., in someembodiments. Impact resistance can be determined according to ASTM D256,in some embodiments. In other embodiments, a 3D article can exhibit animpact resistance of 0.4-1.0 ft·lb/in.

Additionally, 3D articles printed from polymerizable liquids describedherein can exhibit flexural modulus at 25° C. ranging from 1400 to 3500MPa, in some embodiments. Flexural modulus of the 3D article can be 1400to 1700 MPa or 2000 to 3200, in some embodiments.

Moreover, 3D articles printed from polymerizable liquids describedherein can exhibit heat deflection temperatures (HDT) by DMA rangingfrom 110° C. to 190° C., in some embodiments. HDT of a 3D article, forexample can range from 110° C. to 130° C. or 150° C. to 185° C., in someembodiments. As illustrated in the examples below, properties of the 3Darticle can be tailored by varying compositional parameters of thepolymerizable liquid employed to print the 3D article.

These foregoing embodiments are further illustrated in the followingnon-limiting examples.

EXAMPLES

Table 1 provides formulations of polymerizable liquids according to someembodiments described herein.

TABLE I Polymerizable Liquids Formula 3 Formula 4 Formula 5 Formula 2TPU + Polyol + Polyol + Formula 1 TPU + Vinylimidazdol VinylimidazdolVinylimidazdol TPU + Vinylimidazdol & isocyanate & isocyanate &isocyanate Vinylimidazdol & Epoxy HDI HDI HDI TPU 28 Add 90% of add 90%of Formula 1 Formula 1 Acrylate 64.5 64.5 49.5 component Monomeric 5 0.50.5 5 5 curing agent (vinylimidazol) Crosslinking 10 component (Epoxyresin) Crosslinking 15 Component (Core Shell epoxy coated elastomer)Crosslinking 10 10 10 Component (Isocyanate HDI) (Crosslinking 18 18Component) Polyol Photoinitiator 2.5 2.5 2.5 2.5 2.5 colorant 0.02 0.020.02 0.02 0.02 Total % weight 100.02 100.02 100.02 100.02 100.02

Table II shows the physical properties of 3D articles printed usingFormulas 1-5, where Formula 1 was polymerized by exposure to UV light,and Formulas 2-5 were polymerized by exposure to UV light to formcopolymer comprising the acrylate component and monomeric curing agent.Subsequent to 3D article formation, crosslinking via the monomericcuring agent was induced by heating at 110° C. for 2 hours.

TABLE II Physical Properties of Formulas 1-5 Formula 3 Formula 4 Formula5 Formula 2 TPU + Polyol + Polyol + Formula 1 TPU + VinylimidazdolVinylimidazdol Vinylimidazdol TPU + Vinylimidazdol & isocyanate &isocyanate & isocyanate Vinylimidazdol & Epoxy HDI HDI HDI Curing UVonly UV + 2 hrs at UV + 2 hrs at UV + 2 hrs at UV + 2 hrs at 110 C. 110C. 110 C. 110 C. Flexural 1431 1436 1570 1405 1968 Modulus (MPa)Elongation at 6388 4599 6200 5170 6091 break - Tensile strength (psi)Elongation at 225 165 235 177 205 break - Tensile modulus (psi)Elongation at 38 22.3 32.1 42.8 11.8 break -average elongation (%)Impact 1.42 0.82 1.32 0.69 0.32 Resistance - Average (ft. lb./in.)Impact 1.54 0.97 1.48 0.75 0.35 Resistance - Highest (ft. lb./in.)Viscosity at 16520 8300 13460 560 621 30 C. (cps) Tg (C.) 62 28 72Flex-Modulus 1780 1460 1382 at 25 C.

Table III provides formulations of polymerizable liquids according tosome embodiments described herein.

TABLE III Polymerizable Liquids Formula 6 Formula 7 Formula 8 Formula 9Formula10 Formula 11 TPU — — — — — — Acrylate 65.0 50.0 50.0 57.0 62.063.0 component Monomeric 2.5 5.0 5.0 5.0 5.0 4.0 curing agent(vinylimidazol) Crosslinking — — — 35.0 — — component (Epoxy resin)Crosslinking 30 37.0 42.0 — 30.0 30.0 Component (Core Shell epoxy coatedelastomer) Photoinitiator 2.0 2.5 2.5 2.5 2.5 2.5 colorant 0.52 0.520.52 0.52 0.52 0.52 Total % weight 100.02 95.02 100.02 100.02 100.02100.02

Table IV shows the physical properties of 3D articles printed usingFormulas 6-11.

TABLE IV Physical Properties of Formulas 6-11 Formula 6 Formula 7Formula 8 Formula 9 Formula 10 Formula 11 Elongation at 12892 1085610695 5334 11799 11011 break - Tensile strength (psi) Elongation at 401349 348 556 381 360 break - Tensile modulus (psi) Elongation at 6.6 7.14.9 0.8 5.6 7.2 break -average elongation (%) Impact Resistance - 0.620.54 — — 0.49 0.43 Average (ft. lb./in.) Viscosity at 215 — — — — 105 30C. (cps) Tg (C.) 123 — — 113 120 — Flex-Modulus 2153 — — 3155 2143 — at25 C. HDT by DMA (C.) 128 — — 117 120 — HDT 0.46 MPa (C.) 118 — — — — —

Table V provides formulations of polymerizable liquids according to someembodiments described herein.

TABLE V Polymerizable Liquids Formula 12 Formula 13 Formula 14 Formula15 Formula 16 Formula 17 Formula 18 Formula 19 TPU 38.0 33.0 33.0 35.035.0 38.0 38.0 38.0 Acrylate 25.6 43.0 42.0 37.0 36.6 32.6 25.6 27.9component Monomeric 7.0 5.0 6.0 6.0 6.0 7.0 7.0 5.0 curing agent(vinylimidazol) Crosslinking — — — — — — — — component (Epoxy resin)Crosslinking 25.0 15.0 15.0 18.0 18.0 18.0 25.0 25.0 Component (CoreShell epoxy coated elastomer) Photoinitiator 2.5 2.5 2.5 2.5 2.5 2.5 2.52.5 colorant 0.5 0.5 0.5 0.5 0.8 0.8 0.8 0.5 UV absorber 1.4 1.0 1.0 1.01.1 1.1 1.1 1.1 Total % weight 100.0 100.0 100.0 100.0 100.0 100.0 100.0100.0

Table VI shows the physical properties of 3D articles printed usingFormulas 12-19.

Formula 12 Formula 13 Formula 14 Formula 15 Formula 16 Formula 17Formula 18 Formula 19 Elongation at 12733 12398 13198 13226 — 1111810337 11894 break - Tensile strength (psi) Elongation at 424 476 483 464— 485 440 421 break - Tensile modulus (psi) Elongation at 4.2 3.2 3.64.0 — 2.8 3.0 3.9 break - average elongation (%) Impact 0.50 — — 0.44 —0.40 0.55 0.52 Resistance - Average (ft. lb./in.) Viscosity at 520 — — —— — 500 — 30 C. (cps) Tg (C.) 140 — 141 149 141 157 126 155 Flex-Modulus2386 — 2319 2449 2552 2474 2376 2109 at 25 C. HDT by DMA (C.) 177 — 151156 153 160 173 180 HDT 1.82 MPa (C.) 151 124 126 119 131 132 148

All patent documents referred to herein are incorporated by reference intheir entireties. Various embodiments of the invention have beendescribed in fulfillment of the various objectives of the invention. Itshould be recognized that these embodiments are merely illustrative ofthe principles of the present invention. Numerous modifications andadaptations thereof will be readily apparent to those skilled in the artwithout departing from the spirit and scope of the invention.

The invention claimed is:
 1. A polymerizable liquid comprising: anacrylate component; a polymeric additive comprising one or morethermoplastics; and a monomeric curing agent comprising one or moreimidazoles, wherein the acrylate component and the one or moreimidazoles are copolymerizable upon exposure to light, and wherein themonomeric curing agent is present in an amount of 2-20 weight percent.2. The polymerizable liquid of claim 1, wherein the one or morethermoplastics are present in the polymerizable liquid in an amount of10-40 weight percent.
 3. The polymerizable liquid of claim 1, whereinthe thermoplastic comprises multiblock copolymer.
 4. The polymerizableliquid of claim 3, wherein the multiblock copolymer comprisespolyurethane.
 5. The polymerizable liquid of claim 1, wherein the one ormore imidazoles include a point of unsaturation.
 6. The polymerizableliquid of claim 5, wherein the point of unsaturation is an N-vinylmoiety.
 7. The polymerizable liquid of claim 1, wherein the monomericcuring agent is a solvent for the one or more thermoplastics of thepolymeric additive.
 8. The polymerizable liquid of claim 1 furthercomprising a crosslinking component.
 9. The polymerizable liquid ofclaim 8, wherein the crosslinking component comprises epoxy resin, anisocyanate component, a polyol component, or mixtures thereof.
 10. Thepolymerizable liquid of claim 9, wherein the crosslinking component iscoated on particles.
 11. The polymerizable liquid of claim 10, whereinthe particles are elastomeric.
 12. The polymerizable liquid of claim 8,wherein the crosslinking component is present in an amount of 15-50weight percent.
 13. A method of printing a three-dimensional articlecomprising: providing a polymerizable liquid comprising an acrylatecomponent, a polymeric additive comprising one or more thermoplastics,and a monomeric curing agent comprising one or more imidazoles; andirradiating the polymerizable liquid with light to form the article, thearticle comprising a polymeric composite material including thepolymeric additive and copolymer comprising the acrylate component andmonomeric curing agent, wherein the polymerizable liquid is provided ina layer-by-layer process.
 14. The method of claim 13, wherein the one ormore thermoplastics comprise multiblock copolymer.
 15. The method ofclaim 14, wherein the multiblock copolymer comprises polyurethane. 16.The method of claim 13, wherein the polymeric additive is present in thelayer in an amount of 5 to 30 weight percent.
 17. The method of claim13, wherein the article has an impact resistance greater than
 1. 18. Themethod of claim 13, wherein the polymerizable liquid further comprises acrosslinking component.
 19. The method of claim 18, wherein thecrosslinking component comprises epoxy resin, an isocyanate component, apolyol component, or mixtures thereof.
 20. A method of printing athree-dimensional article comprising: providing a polymerizable liquidcomprising an acrylate component, a polymeric additive comprising one ormore thermoplastics, a monomeric curing agent comprising one or moreimidazoles, and a crosslinking component; and irradiating thepolymerizable liquid with light to form the article, the articlecomprising a polymeric composite material including the polymericadditive and copolymer comprising the acrylate component and monomericcuring agent, wherein the crosslinking component comprises epoxy resin,an isocyanate component, a polyol component, or mixtures thereof, andwherein the crosslinking component is coated on particles.
 21. Themethod of claim 18 further comprising crosslinking the copolymer and theone or more thermoplastics of the polymeric additive with thecrosslinking component.
 22. The method of claim 21, wherein thecrosslinking is initiated by reaction of the one or more imidazoles ofthe monomeric curing agent with the crosslinking component.
 23. Themethod of claim 22, wherein the reaction is activated by heat.
 24. Themethod of claim 21, wherein the article is black in color.
 25. Themethod of claim 24, wherein black pigment is not added to thepolymerizable liquid.